Coatings have been provided for seeds for a variety of reasons such as increasing water absorption, preventing premature germination, protecting the seed with pesticides, etc. It is required that seed coatings include a coloring agent, such as a dye, so that an observer can immediately determine that the seeds are treated. The purpose of such coloring is, of course, to prevent seed, which may have coated thereon toxic pesticides or the like, from being intermixed with seed, e.g., grain or oilseed, which might be ingested or otherwise exposed to humans or farm animals.
The coloring of coated seed has been found to be advantageous for reasons other than safety reasons. The colored coating is useful to indicate to the manufacturer and consumer the degree of uniformity of the coating applied where uniformity of coating is important, e.g., seeds coated to delay germination. The coloring may serve to hide blemishes which affect the appearance but not the quality of germination of the seed and thereby make the seed more acceptable to consumers. Coloring makes the seed more visable so that it is easier for the planter to ascertain that his equipment is depositing seed in the ground.
The colorings which are commonly used in conjunction with seed coatings have usually resulted in a translucent colored seed coating which, though generally sufficient for distinguishing coated seed from non-coated seed, may be too faint to easily determine the uniformity of coating, to hide seed blemishes or to be clearly visible in contrast to the soil from atop farm machinery. Many seeds have a dark brown or black color on which translucent colored coatings show up poorly. Variegated or mottled seeds such as sunflower seeds may appear to be unevenly coated if coated with a weakly colored coating. Furthermore, while one experienced with seed easily recognizes the foreign color, for coated seeds sold to the uninitiated, such as home gardeners, it is important that coated seeds have distinct coloring so that there is no mistaking the presence of foreign substance thereon.
Various factors may affect the coloring in seed coatings after the coatings have been applied to the seeds. The color may be masked by subsequent additional treating or overtreating coated seeds. The pH of the seed surface may adversely affect the coloring agents in seed coatings.
Accordingly, it would be desirable to provide seeds having coatings with increased opacity and brightness. The coloring should adhere to the seeds during storage and shipping and should remain distinct on the seed even if subsequent coatings are applied to the seed.